There are a couple of ways of selecting the sheets.
Either using the Replace argument or by building an array of sheetnames.

Private Sub SelectSheets_Click()

    Dim blnReplace As Boolean
    Dim lngRow As Long
    
    blnReplace = True
    For lngRow = 3 To 21
        If Cells(lngRow, 2) = "Y" Then
            Sheets(Cells(lngRow, 1).Value).Select blnReplace
            blnReplace = False
        End If
    Next
    MsgBox "Using Replace"
    
    Me.Select   ' clear selection
    
    Dim lngNSheets As Long
    Dim lngCount As Long
    
    lngNSheets = Application.WorksheetFunction.CountIf(Range("B3:B21"), "Y")
    ReDim vntSheets(1 To lngNSheets) As Variant
    
    For lngRow = 3 To 21
        If Cells(lngRow, 2) = "Y" Then
            lngCount = lngCount + 1
            vntSheets(lngCount) = Cells(lngRow, 1)
        End If
    Next
    Sheets(vntSheets).Select
    MsgBox "Using array"
    
End Sub